In Japanese Patent Application Laid-Open 61-150249, a ring-like contact pin of thin wall construction is proposed for use in an IC socket which is used for mounting an IC device or similar electronic parts (see FIG. 17). In an IC socket, as shown in FIGS. 18 and 19, the leads of an IC device positioned on top 3 of a multiple contact pin 10' (FIG. 17) and aligned on a socket body 20 are pressed toward contact pin 10' by pads 21-1 and 21-2 fitted on cover 21 linked on socket body 20 by shaft 23 as the cover is closed.
However prior art pins similar to contact pins 10' have the disadvantage of poor electrical connection due to an insulation of oxide film formed on the surfaces of the leads; and each contact pin 10', when pads 21-1 and 21-2 fitted on cover 21 are pressed for connections of the leads and contact pins 10' as cover 21 is closed.
Also, prior art contact pins similar to contact pin 10' have the disadvantage that they are too weak to endure severe plastic deformation as they are made of ring plates having a very thin wall.
In view of the foregoing, it is an object of the present invention to provide multiple contact pins of very thin wall construction and having good electrical connection for an IC socket without an oxide film insulation likely being formed on the surface of leads and contact pins and without breaking due to plastic deformation.
Further, prior art IC sockets having mount contact type contact pins 10' have the disadvantage that it is hard to align the leads of the IC device in positions between guide walls provided in the IC socket. Furthermore, it has a disadvantage that the leads may be bent or broken if deformed when the cover 21 is closed.
Accordingly, it is another object of the present invention to provide an IC socket that has a feature for preventing the position of an IC device from deviating and its leads from being deformed. This allows the IC device to be automatically positioned for secure contact between contact pins with lead frames by simply placing the IC device in a limited range on a stage.
In recent IC sockets, numerous contact pins have to be aligned at intervals closer than usual as the IC devices are made more dense in order to make camera-equipped VTRs, portable telephone sets, and similar electronic devices smaller and with increased features. Such finer alignment leads have a more difficult task of forming the guide walls for positioning the contact pins and guiding and restricting the contact action of the contact pins with leads.
There is a disclosure about a connector for an IC mounting board in Japanese Utility Model Application Laid Open Sho 58-70687. In the disclosed connector there are projected contact portions for mounting pins of the IC mounting board on free ends of elastic contact arms. Guide pieces project in the vicinity of the contact portions. The guide pieces are positioned in guide grooves (guide walls) formed on a socket body to guide elastic displacements of the elastic contact arms. A feature of the connector is the easy forming of a socket body as the elastic contact arms corresponding to the contact pins can be partly guided on their front free ends and rear fixed ends.
The inventors have also proposed multiple contact pins of very thin wall construction having securing strength at very close intervals for an IC socket in the Japanese Utility Model Application Hei 3-41476. The contact pins, as shown in FIG. 1 have a ring-like contact arm 2 formed of a pair of arm portions 2a and 2b opposing each other. Contact arm 2 also has contact portion 3 formed at its front free end to contact a lead of an IC device (not shown). Contact arm 2 is connected with the base of contact pin 10 by way of neck 1 on its rear fixed end.
Contact pin 10 can have a secure contact action with the lead of an IC device without twisting at its arm portions 2a and 2b, even if it is formed as a very thin construction. This is because force F, exerted downward toward contact pin 10, as shown in FIG. 2, is dispersed up and down by the pair of opposed arm portions 2a and 2b.
However, the prior IC socket described above has the disadvantage that adjacent contact pins 10 may likely contact each other as they tend to easily flex in an aligning direction, although they have enough vertical strength to endure force F as described above. As contact pins 10 are embedded in the socket body, it is difficult to prevent them from making contact at their mid portions in the construction of the connector of Japanese Utility Model Application Laid Open Sho 58-70687 described above where the elastic contact arm is guided by its front free end and rear fixed end.
Accordingly, it is still another object of the present invention to provide an IC socket that allows contact pins aligned at very close intervals to securely move.
The contact pins of a conventional IC socket shown in FIG. 18 are usually 0.2 to 0.4 mm thick. In order to prevent adjacent contact pins from touching each other, the IC socket has multiple guide walls provided therein. Since the guide walls are aligned at relatively wide intervals, they are made of synthetic resin and integrated in the socket body.
As described above, the contact pins are designed so that as force F is exerted down on the top portion of any of the contact pins, it can be effectively dispersed by the arm portions. The contact pins can be made to securely contact the leads of the IC device even when the contact pins are as thick as 0.13 to 0.18 mm.
However, although the contact pins of a conventional IC socket can be made thin, it is extremely difficult to align them at very narrow intervals as the multiple guide walls are made of synthetic resin to integrate with the socket body. In other words, the guide walls may have insufficient filling with a molding material when injection-molded.
In view of this, it is still another object to provide an IC socket that can be molded and assembled easily and effectively for an increased number of pins of an IC device aligned at narrower intervals.